The Church on the eve of reform and the ninety-five theses were the precursors to the famous, boring Protestant Reformation. They helped foster it and make it grow.
The Church on the eve of the Reformation was a sort of mix-up. Good and bad lived together hand in hand. The bad side was really bad.
For example, bishops ruled over areas of land called dioceses. They recently had been given more than one diocese. They lived and stayed in only one, yet collected the incomes of all the others. Complete corruption was manifest in this aspect.
Parish priests–meaning regular priests in a typical church–were completely ignorant. This was not their fault, since there were no seminaries (schools) where to educate them. They only knew how to hold Mass and how to pray simply.
All priests were told by the pope to hold Mass at least four times a year! Now, priests are supposed to hold Mass every day, so to tell them to hold Mass four times a year, well, one can imagine how bad things were.
On the other hand, the good hand, clerics were performing more popular acts of piety for the people to see. It could have been an effort of popularization, but again, it may not have been.
The ninety-five theses that Martin Luther nailed on the church door in Wittenberg were a complaint about the condition of the Church. He argued and challenged the Church about its practices. They were especially centered on indulgences and the justification of the opposition to the indulgences.
Indulgences were a slip of paper that the pope sold that was supposed to let you skip your time in Purgatory. Under it all, though, was just another effort by the pope to raise money.
The Church had a lot of corruption but it also had some good aspects. One may outweigh the other, but they lived together side by side. The ninety-five theses triggered the start of the Protestant Reformation.